//
// Created by martin on 4/13/22.
//

#ifndef MUDUO_THREADLOCALSINGLETON_H
#define MUDUO_THREADLOCALSINGLETON_H

#include "muduo/base/noncopyable.h"

#include <assert.h>
#include <pthread.h>

namespace muduo
{

template<typename T>
class ThreadLocalSingleton : noncopyable
{
public:
    ThreadLocalSingleton() = delete;
    ~ThreadLocalSingleton() = delete;

    static T& instance()
    {
        if (!t_value_)
        {
            t_value_ = new T();
            deleter_.set(t_value_);
        }
        return *t_value_;
    }

    static T* pointer()
    {
        return t_value_;
    }

private:
    static void destructor(void* obj)
    {
        assert(obj == t_value_);
        typedef char T_must_be_complete_type[sizeof(T) == 0 ? -1 : 1];
        T_must_be_complete_type dummy; (void)dummy;
        delete t_value_;
        t_value_ = 0;
    }

    class Deleter
    {
    public:
        Deleter()
        {
            pthread_key_create(&pkey_, &ThreadLocalSingleton::destructor);
        }
        ~Deleter()
        {
            pthread_key_delete(pkey_);
        }

        void set(T* newObj)
        {
            assert(pthread_getspecific(pkey_) == NULL);
            pthread_setspecific(pkey_, newObj);
        }

#if 0
        T* get()
        {
            return static_cast<T*>(pthread_getspecific(pkey_));
        }
#endif

        pthread_key_t pkey_;
    };

    static __thread T* t_value_;
    static Deleter deleter_;
};

template<typename T>
__thread T* ThreadLocalSingleton<T>::t_value_ = 0;

template<typename T>
typename ThreadLocalSingleton<T>::Deleter ThreadLocalSingleton<T>::deleter_;

} // namespace muduo

#endif //MUDUO_THREADLOCALSINGLETON_H
